Electric switch



Aug. 2.5,-1931. MENZEL 1,820,361

ELECTRI-C SW-ITCH I Filed D80. 20, 1928 fag/t Patented Aug. 25, 1931 UNITED STATES PATENT OFFICE FRIEDRICH MENZEIIJ, OF STUTTGART, GERMANY, ASSIGNOR TO ROBERT BOSCH AKTIEN- GESELLSCHAFT, F STUTTGART, GERMANY ELECTRIC Application filed December 20, 1928, Serial No.

The present invention relates to electric switches and more particularly to a combined electro-magnetic regulator and switch for electrical systems of vehicles.

In electrical systems of vehicles having a dynamo and battery, an electro-magnetio switch is located therebetween and is provided with current and voltage coils for automatically controlling the connections of the 4 battery charging circuit of the dynamo.

Upon the occurrence of a short-circuiting of the leads connected between the automatic switch and the current consuming devices, the switch opens and closes alternately at definite intervals. Since -the current coil, which is of suitable dimensions, assists the voltage coil after the switch has closed, the said switch is only opened after a considerable drop in voltage. On the other hand, owing 1a to the low voltage on opening of the switch, the dynamo requires a certain amount of time in order to return the final voltage.

When a switch of this type is combined with a regulator so that the two have a com- Mon current coil, the said current coil must be kept small, corresponding to the requirements of the regulator. The automatic switch consequently opens and closes in rapid succession upon short-circuiting as above de- 3 scribed, so that the switch spring and its contacts are damaged by the intermittent sparks formed thereby.

This disadvantage is overcome according to the invention by the provision of a suit- 5 ably arranged switch contact spring consisting of bi-metal strips which are affected by the heat of the sparks formed on opening the switch.

A combined regulator switch with a single 0 armature for electrical systems of vehicles is shown in the drawings as one form of construction of the invention.

Figure 1 shows the regulator switch partly an section together with a wiring diagram,

Figure 2 is a section on an enlarged scale of a portion of the regulator switch when the switch contact spring is heated.

A compound wound relay in the, form of D an iron core 2, about which are'wound a our- SWITCH 327,428, and in Germany December 17, 1927.

rent coil 3, and a voltage coil 4 is mounted on the base of an angle iron frame 1. An armature 5 is carried by a leaf spring 6 mounted on the frame 1, and in its position of rest contacts with a stop 7 insulatedly mounted on the iron core 2. A bi-metal or temperature compensating spring 8, carrying on the one hand a contact 9, and on the other a brass angle member 10, is secured to the base of the iron frame 1.

The member 10, by reason of the resiliency of the spring 8, bears against an arm'll of the armature 5, the arm being bent at right angles to said armature.

The contact 9 is located opposite a contact 12 which is mounted on an insulating plate 13 secured to the frame 1. The contacts 9 and 12 form the switch contacts.

A stop 14 is provided on the arm 11 of the armature and is located opposite a stop 16 of insulating material mounted on a contact spring. 15. The contact spring carries at its end a contact 17, which is adapted to cooperate with a pairof stationary contacts 18 and 19. The contacts 17, 18 and.19 serve as the regulator contacts.

An excitation winding 21 is connected with the positive terminal of a dynamo armature 20 in series with-a series resistance 22, the free end of which is earthed' A lead 23 is taken off between the excitation winding 21 and the resistance 22, and led to the contact spring 15 mounted on the insulating plate 13, thereby short-circuiting the resistance 22 when the contacts 17, 18 are closed,

as the contact 18 is earthed.

One end of each of the coils 8 and 4 is connccted with the positive terminal of the armature 20. The other end of the coil 3 is connected with the bi-metal spring 8, whilst the other end of the coil 4 is earthed. Leads are taken from the switch contact 12 to the positive terminals of the battery 24 and .the lamps 25, the negative terminals of which and also the negative terminal of the armature 20 are all earthed.

The regulator switch normally works as follows Upon the dynamo voltage reaching a predetermined value, the armature 5 is attracted by the iron core 2 by the excitation of the voltage coil 4, to such an extent that the contact 9 of the bi-metal spring 8 bears against the stationary contact 12, thereby closing the switch and connecting up the current consuming devices 24 or 25 with the dynamo.

On further increase of the dynamo voltage, the contact spring 15 is moved by the stop 14, so that the contacts 17, 18 are first opened andthen the contacts 17 19 closed. In the last position, the excitation windin 21 is short-circuited through the lead 23, t e contact spring 15, the contacts 17 and 19, leaf spring 6, iron frame 1, bi-metal spring 8 and coil 3.

If, during the operation, short-circuit occurs in the leads from the switch contact 12 to the current consuming devices 24, 25 the value of the current produced by the dynamo 20, 21 rapidly rises, whilst its voltage drops. The automatic switch consequently opens the contacts 9, 12. The dynamo consequently immediately returns to the normal voltage, and the automatic switch closes again, the op eration then being repeated in very rapid sequence. The sparks caused on opening the switch contacts rapidly heat the bi-metal spring 8. This bends to the right on expansion, so that the switch contacts 9, 12 are opened (Fig. 2). After a certain time, during which the dynamo voltage is maintained constant in the usual manner by the regulator 17, 18, 19, the bi-metal spring 8 cools down and resumes its normal position.

The switch contacts 9, 12 are thereby closed again as the armature 5 is attracted b the iron core 2 according to the dynamo vo tage. After the switch has closed, as already described the rapid successive opening and closing of the switch commences, owing to the short-circuit, with the sole difference that the bi-metal spring now heats up more rapidly than on the first occasion, since it has not completely cooled on closing of the switch. The heat produced by small opening sparks is therefore sufiicient to cause the bi-metal spring to bend again. The operation of the switch proceeds in this manner without its contacts being damaged by the relatively small sparks on opening.

Owing to the fact that a part of the bimetal strip lies adjacent and immediately below the gap between the switch contacts 9, 12, it is particularly exposed to the sparks set up on opening of the switch and is rapidly heated thereby. The heat of the first sparks, which last for a compartively long time, is conducted away from the contact 9 by the brass angle member 10, so that it is not too highly heated. Further, the brass angle member stores up the heat and thereby retards the cooling of the bi-metal spring. The bi-metal spring 8 is silvered in order to prevent oxide formed on heating and has a low electrical conductivity, improving the electrical connection between the bi-metal spring and the contact member 9. The oxidation of the silver has no adverse efiect, as silver oxide is a good electrical conductor.

In the present example, the bi-metal spring consists of strips of iron and brass welded together, the brass strip being located on the side facing the contact 9. The period during which the switch is open can be shortened by selecting a suitable composition of the bimetal spring.

The sequence of switching operations is thereby rendered more rapid, and the striking of the armature 5 against the end of the core 2, or against the stop 7 can be used as an audible indication to warn the driver of the short-circuit.

Instead of using the bi-metal spring to prolong the opening of the switch, it can also be used to prolong the closing of the switch and thus to avoid continuous sparks. For this purpose it is only necessary to reverse the position of the two welded strips of the bi-metal spring, so that the iron strip is located on the side facing the switch contact 9.

What I claim is 1. In a battery charging system, including a dynamo, dynamo voltage regulating means, a battery and current consuming devices, the combination of an automatic safety switch comprising a compound wound relay, an armature actuated by said relay, a main circuit from said dynamo to said current consuming devices and thermo-sensitive contact means situated in said main circuit, mechanically operated by said armature to open and close said main circuit and operated in response to heat generated by sparks in its actuation to actuate the switch contacts independently of the mechanical operation of said armature.

2. In a battery charging system, including a dynamo, dynamo voltage regulating means, a battery, current consuming devices and a main circuit from said dynamo to said current consuming devices, the combination of an automatic safety switch comprising thermo-sensitive contact means in said-main circuit, a compound wound relay common to both said dynamo voltage regulating means and to said thermo-sensitive contact means and an armature actuated by said relay for operating said dynamo voltage regulating means and said thermo-sensitive contact means, said thermosensitive contact means being arranged to open the main circuit independently of said armature in response to heat generated by the sparking of the contacts.

3. In a battery charging system, including a dynamo, dynamo voltage regulating means, a battery, current consuming devices and a main circuit from said dynamo to said current consuming devices, the combination of and an armature actuated by said relay adapted to displace said thermo-sensitive switch to make and breaksaid main c1rcu1t,sa1dthermo sensitive switch being arranged to break said main circuit independently of the armature in response to variations in temperature caused by sparking of said switch.

4. In a battery charging system, including a dynamo, a regulator adapted to maintain constant the dynamo voltage, a battery, current consuming devices and a main circuit from said dynamo to said current consuming devices, the combination of an automatic safety switch comprising acompound wound relay, an armature actuated by said relay, a pair of contacts in said main-circuit and a thermo-sensitive switch element carrying one of said contacts and affected by the heat generated by sparks set up on displacement of said switch on opening said contacts.

5. In a battery charging system, including a dynamo, a regulator adapted to maintain constant the dynamo voltage. a battery, current consuming devices and a main circuit from said dynamoto said current consuming devices, the combination of an automatic safety switch comprising a compound wound relay, an armature actuated by said relay, a pair of contacts in said main circuit and a resilient bi-metal switch carrying one of said contacts and affected by the heat generated by sparks set up on displacement of said switch to open said contacts.

6. In a battery charging system, including a dynamo, dynamo voltage regulating means, a battery, current consuming devices and a main circuit from said dynamo to said current consuming devices, the combination of an automatic safety switch comprising a thermo-sensitive bi-metal spring switch situated in said main circuit, a compound wound relay common to said dynamo voltage regulating means and to said switch, an armature actuated by said relay and a pair of contacts in said main circuit, one of which is carried by said switch, said switch being arranged to move the contact carried by it away from the other of said pair of contacts in response to an increase of temperature in said switch caused by sparking between said pair of contacts.

7 In a battery charging system, includinga dynamo, dynamo voltage regulating means, a. battery, current consuming devices and a main circuit from said dynamo to said current consuming devices, the combination of an automatic safety switch comprising a coinpound wound relay, an armature actuated by said relay, a pair of contacts in said main circuit for operation by said armature and a thermo-sensitive bi-metal spring switch, a

portion of which is situated adjacent the gap between said contacts when these are open, the end of said switch carrying one of said contacts, said switch being arranged to move the contact carried by it-away from the other of said pair of contacts in response to an increase of temperature in said switch caused by sparking between said pair of contacts.

8. In a battery charging system, including a dynamo, dynamo voltage regulating means,

a battery, current consuming devices and a main circuit from said dynamo to said current consuming devices, the combmation of an automatic safety switch comprlslng an angle iron frame, a compound wound relay supported on said frame, an armature actuated by said relay, spring means for supporting said armature on said frame, insulating means for supporting said dynamo voltage regulating means on said angle iron frame and a thermo-sensitive switch means situated in said main circuit and supporied at one end on said frame, said thermo-sensitive switch means being arranged to be mechanically operated by said armature, and to open said main circuit independently of said armature upon an increase in temperature caused by sparking of said switch.

9. In a battery charging system, including a dynamo, dynamo voltage regulating means, a battery, current consuming devices and a main circuit from said dynamo to said current consuming devices, the combination of an automatic safety switch comprising an angle iron frame, a compound wound relay supported on said frame, an armature actuated by said relay and resiliently mounted on said frame, a contact arm for said dynamo voltage regulating means, insulating means for supporting said contact arm on said angle iron frame, a pair of contacts in said main circuit, and a thermo-sensitive switch carrying one of said contacts and mounted at one end of said frame, said thermo-sensitive switch being arranged to be mechanically operated by said armature, and to open said main circuit independently of said armature upon an increase in temperature caused by sparking of said switch.

10. In a battery charging system, including a dynamo, dynamo voltage regulating means,

a battery, current consuming devices and a mam circuit from said dynamo to sand current consuming devices, the combination of said bi-metal spring by sparking of said switch will open said contacts independently of the armature.

11. In a battery charging system, including a dynamo, dynamo Voltage regulating means, a battery, current consuming devices and a main circuit from said dynamo to said can rent consuming devices, the combination of an automatic safety switch comprising an angle iron frame member, a compound wound relay mounted on said frame member, an armature actuated by said relay, a right angled flanged portion of said armature, a contact arm of said dynamo voltage regulating means, insulating means for mounting said contact arm on said angle iron member, a contact on said flanged portion of said armature for displacing said contact arm between the contacts of said dynamo voltage regulating means, a pair of contacts in said main circuit, a thermo-sensitive bi-metal spring carrying one of said contacts and supported by said angle iron member and an element of thermo-conductivity connected with said bi-metal spring adjacent its contact for engagement with said flanged member of said armature, said bi-metallic spring being arranged to separate said contacts independently of said armature in response to heat caused by sparking of said switch.

In testimony whereof I have hereunto affiXed by signature.

FRIEDRICH MENZEL. 

